Intervertebral implant

ABSTRACT

A vertebral implant for fusing adjacent vertebrae or for replacing vertebral bodies is disclosed. The implant is a biocompatble metal resorbable or radiolucent implant conforming substantially in size and shape with an end plate of a vertebra. The implant preferably has a wedge-shaped profile to restore disc height and the natural curvature of the spine. The top and bottom surfaces of the implant have areas with a plurality of teeth to resist expulsion and provide initial stability and areas devoid of any protrusions to receive implantation instrumentation. The implant also has a stackability feature. The implant provides initial stability needed for fusion without stress shielding.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. application Ser.No. 13/537,186, filed Jun. 29, 2012, which is a continuation of U.S.application Ser. No. 11/672,593, filed Feb. 8, 2007, now U.S. Pat. No.8,231,675, which, in turn, is a continuation of U.S. application Ser.No. 10/322,609, filed Dec. 19, 2002, now U.S. Pat. No. 7,192,447, theentireties of which are incorporated by reference herein.

FIELD OF THE INVENTION

This invention relates to an artificial biocompatible vertebral deviceand, more particularly, to an intervertebral spinal implant for use inthe treatment of back pain.

BACKGROUND OF THE INVENTION

A number of medical conditions such as compression of spinal cord nerveroots, degenerative disc disease, tumor, and trauma can cause severeback pain. Intervertebral fusion is one surgical method of alleviatingback pain. In intervertebral fusion, two adjacent vertebral bodies arefused together by removing the affected intervertebral disc andinserting an implant that would allow for bone to grow between the twovertebral bodies to bridge the gap left by the disc removal. Anothersurgical method of relieving back pain is by corpectomy. In corpectomy,a diseased or damaged vertebral body along with the adjoiningintervertebral discs are removed and replaced by a spinal implant thatwould allow for bone to grow between the closest two vertebral bodies tobridge the gap left by the spinal tissue removal.

A number of different implant materials and implant designs have beenused for interbody fusion and for vertebral body replacement withvarying success. Current implant materials used include metals,radiolucent materials including plastics, elastic and polymericmaterials, ceramic, and allografts. Current implant designs vary fromthreaded cylindrical implants to rectangular cages with teeth-likeprotrusions.

For example, U.S. Pat. No. 5,782,919 to Zdeblick et. al. discloses aninterbody fusion device which has a tapered body defining a hollowinterior for receiving a bone graft or bone substitute material.Furthermore, the body of the device defines exterior threads forgripping the adjacent vertebrae and has a series of vascularizationopenings for promoting bony ingrowth. A variant on this design is shownin U.S. Pat. No. 4,961,740 to Ray et, al. The Ray patent illustrates ahollow, cylindrical fusion cage having a helical thread disposed on theouter surface of the cage with a plurality of holes leading to thehollow center between the threads.

U.S. Pat. No. 5,766,252 to Henry et. al. discusses a rectangularinterbody spinal spacer that has vertically opposite upper and lowerload bearing surfaces spaced apart a distance corresponding to thedesired spacing. The rigid member has a wedge-shaped configuration withan ogival tip at the front end of the member.

While each of the foregoing prosthesis, address some problems relatingto intervertebral disc replacements or vertebral body and intervertebraldisc replacements, they present others. Thus, there is a need for anintervertebral implant whose design takes into consideration the anatomyand geometry of the intervertebral space sought to be filled by theintervertebral prosthesis as well as the anatomy and geometry of the endplates of the adjacent vertebral bodies. There is also a need for aspinal disc implant which integrates well with the vertebral bone tissueof the adjacent vertebral bodies between which the implant is to beinserted.

SUMMARY OF THE INVENTION

The present invention relates to an intervertebral implant for use whensurgical fusion of vertebral bodies is indicated. The implant may beused to replace a diseased or damaged intervertebral disc or may be usedto replace a diseased or damaged partial or complete vertebral body, ormay be used to replace a diseased or damaged vertebral body and adjacentintervertebral discs.

In one embodiment, the implant comprises a body made from abiocompatible metal, radiolucent maternal, allograft, or resorbablematerial conforming substantially in size and shape with the end platesof the vertebrae, has a wedge-shaped profile, and has a central bore forreceiving an osteoconductive material to promote the formation of newbone. The top and bottom surfaces may be flat planar surfaces, wedged,or curved surfaces. Preferably, the top and bottom surfaces mimic thetopography of the vertebral end plates. The top and bottom surfaces eachmay have areas extending from an outer periphery of the implant to thecentral bore having a plurality of teeth for engaging the end plates ofadjacent vertebra and each may also have areas extending from the outerperiphery of the implant to the central bore that are substantiallysmooth for receiving a surgical instrument. The substantially smoothareas may extend in an anterior-posterior direction, a lateraldirection, or may run in both directions. In addition, the substantiallysmooth area may run in an anterio-lateral direction.

The implant may have at least one channel on at least one side of theimplant for receiving a surgical toot or instrument. This channel mayalso extend in at least an anterior-posterior direction, a lateraldirection, or in both directions.

In another embodiment, instead of instrument receiving channels, theimplant may have a threaded hole on the anterior, anterio-lateral, orlateral side of the implant for receiving a threaded arm of an Insertiontool.

In yet another embodiment, the implant may have a stackability featurewherein the implant is modular and comprises an upper endcap, and alower endcap; or an upper endcap, a lower endcap, and at least one bodyportion.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top view of a first embodiment of the implant according tothe present invention;

FIG. 2 is a cross-sectional side view of the implant of FIG. 1;

FIG. 3 is an axial cross-sectional view of the implant of FIG. 1;

FIG. 4 is a front or anterior view of the implant of FIG. 1;

FIG. 4A is a top view of a another embodiment of the implant of FIG. 1;

FIG. 4B is a top view of a another embodiment of the implant of FIG. 1;

FIG. 5 is a top view of a second embodiment of the present invention;

FIG. 6 is a cross-sectional side view of the implant of FIG. 5;

FIG. 7 is an axial cross-sectional view of the implant of FIG. 5;

FIG. 8 is a front or anterior view of the implant of FIG. 5;

FIG. 9 is a top view of a third embodiment of the present invention;

FIG. 10 is a side view of the implant of FIG. 9;

FIG. 11 is an axial cross-sectional view of the implant of FIG. 9;

FIG. 12 is a front or anterior view of the implant of FIG. 9;

FIG. 13 is a top view of a fourth embodiment of the present invention;

FIG. 14 is a side view of the implant of FIG. 13;

FIG. 15 is an axial cross-sectional view of the implant of FIG. 13;

FIG. 16 is a front or anterior view of the implant of FIG. 13;

FIG. 16A is a perspective view of a fifth embodiment of the presentinvention;

FIG. 17 is a top view of an upper endcap of the implant of FIG. 164A

FIG. 18 is a bottom view of the upper endcap of FIG. 17;

FIG. 19 is a cross-sectional view taken at line A-A of the upper endcapof FIG. 17;

FIG. 20 is a cross-sectional view taken at line B-B of the upper endcapof FIG. 17;

FIG. 21 is a front or anterior view of the upper endcap of FIG. 17;

FIG. 22 is a top view of a lower endcap of the implant of FIG. 16A;

FIG. 23 is a bottom view of the lower endcap of FIG. 22;

FIG. 24 is a cross-sectional view taken at line A-A of the tower endcapof FIG. 22;

FIG. 25 is a cross-sectional view taken at line B-B of the tower endcapof FIG. 22;

FIG. 26 is a front or anterior view of the lower endcap of FIG. 22;

FIG. 27 is a top view of an alternate upper endcap of a fifth embodimentof the present invention;

FIG. 28 is a bottom view of the upper endcap of FIG. 27;

FIG. 29 is a cross-sectional view taken at line A-A of the upper endcapof FIG. 27;

FIG. 30 is a cross-sectional view taken at line B-B of the upper endcapof FIG. 27;

FIG. 31 is a front or anterior view of the upper endcap of FIG. 27;

FIG. 32 is a top view of an alternate lower endcap of a fifth embodimentof the present invention;

FIG. 33 is a bottom view of the lower endcap of FIG. 32;

FIG. 34 is a cross-sectional view taken at line A-A of the lower endcapof FIG. 32;

FIG. 35 is a cross-sectional view taken at line B-B of the tower endcapof FIG. 32;

FIG. 36 is a front or anterior view of the lower endcap of FIG. 32;

FIG. 37 is a front or anterior view of a body portion of the implant ofFIG. 16A;

FIG. 38 is a cross-sectional view taken at line A-A of the body portionof FIG. 37;

FIG. 39 is a top view of the body portion of FIG. 37;

FIG. 40 is a bottom view of the body portion of FIG. 37;

FIG. 41 is a cross-sectional view taken at line B-B of the body portionof FIG. 37;

FIG. 42 is a top view of an endcap of a sixth embodiment of the presentinvention;

FIG. 43 is a bottom view of the endcap of FIG. 42;

FIG. 44 is a cross-sectional view taken at line A-A of the endcap ofFIG. 42;

FIG. 45 is a side or lateral view of the endcap of FIG. 42;

FIG. 46 is a front or anterior view of the endcap of FIG. 42;

FIG. 47 is a top view of an alternate endcap of a sixth embodiment ofthe present invention;

FIG. 48 is a bottom view of the endcap of FIG. 47;

FIG. 49 is a cross-sectional view taken at line A-A of the endcap ofFIG. 47;

FIG. 50 is a side or lateral view of the endcap of FIG. 47;

FIG. 51 is a front or anterior view of the endcap of FIG. 47;

FIG. 52 is a top view of an alternate endcap of a sixth embodiment ofthe present invention;

FIG. 53 is a bottom view of the endcap of FIG. 52;

FIG. 54 is a cross-sectional view taken at line B-B of the endcap ofFIG. 52;

FIG. 55 is a side or lateral view of the endcap of FIG. 52;

FIG. 56 is a front or anterior view of the endcap of FIG. 52;

FIG. 57 is a top view of a body portion of a sixth embodiment of thepresent invention;

FIG. 58 is a bottom view of the body portion of FIG. 57:

FIG. 59 is a cross-sectional view of the body portion of FIG. 57;

FIG. 60 is a cross-sectional view taken at line B-B of the body portionof FIG. 57;

FIG. 61 is a front or anterior view of the body portion of FIG. 57;

FIG. 62 is a side or lateral view of the body portion of FIG. 57;

FIG. 63 is a top view of an endcap of a seventh embodiment of thepresent invention;

FIG. 64 is a bottom view of the endcap of FIG. 63;

FIG. 65 is a cross-sectional view taken at line A-A of the endcap ofFIG. 63;

FIG. 66 is a side or lateral view of the endcap of FIG. 63;

FIG. 67 is a top view of a body portion of a seventh embodiment of thepresent invention;

FIG. 68 is a bottom view of the body portion of FIG. 67;

FIG. 69 is a side or lateral view of the body portion of FIG. 67; and

FIG. 70 is a perspective view of an implant of a seventh embodiment ofthe present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a top view of a first embodiment of intervertebral spaceror implant 10 according to the present invention. Implant 10 has agenerally kidney-bean shaped footprint which includes anterior side 12,posterior side 14, and first and second lateral sides 16, 18. Anteriorside 12 and lateral sides 16, 18 are all substantially arcuate,preferably convex, in shape while posterior side 14 is substantiallyarcuate, preferably concave, in shape.

Implant 10 further includes central bore 26 which can be filled withbone growth inducing substances to allow bony ingrowth and to furtherassist in the fusion of the adjacent vertebrae and the implant. Centralbore 26 has a generally kidney-bean shape that substantially conforms tothe kidney-bean shaped footprint of implant 10. The radius of curvature23 of the arcuate, preferably convex, sides of central bore 26 may beabout 6.5 mm to about 8.5 mm, preferably about 7.5 mm, and the radius ofcurvature 25 of the areas between the preferably convex and concavesides are about 3 mm to about 3.4 mm, preferably about 3.2 mm.

In addition, implant 10, on its upper 15 and tower 30 surfaces, hassections or areas having teeth 20, spikes, or similar grippingstructures to facilitate engagement of implant 10 with the end plates ofthe adjacent vertebra. The teeth may be pyramidal, saw toothed or othersimilar shapes. Ridges may also be used to facilitate gripping adjacentvertebrae. Implant 10 may also have sections or areas 22 or 24 or bothwhich are essentially smooth and devoid of any protrusions. Sections 22,24 are provided to assist the surgeon in implantation of the spacer aswill be discussed below.

As mentioned above, implant 10 has a generally kidney-bean shapedfootprint. This footprint is designed to conform in size and shape withthe general perimeter and shape of the end plates of the vertebraebetween which implant 10 is to be implanted thereby providing maximumsupport while avoiding the intravertebral foramen of the vertebralbodies. The intravertebral foramen or the spinal canal is the portion ofthe vertebral body that houses the spinal cord and nerve roots.Generally, a portion of the intravertebral foramen extends into the bodyportion or end plate portion of the vertebra. This portion of theintravertebral foramen, in effect, changes the perimeter of the bodyportion of the vertebra from substantially an oval shape tosubstantially a kidney-bean shape. Accordingly, the footprint of implant10 is kidney-bean shaped to emulate the general shape and perimeter ofthe body portion of the adjacent vertebrae.

Implant 10 preferably also has a generally wedge-shaped, side-viewprofile that is designed to restore the natural curvature or lordosis ofthe spine after the affected disc or affected vertebral body andadjoining discs have been removed. As shown in FIGS. 2 and 4, this wedgeshape results from a gradual increase in height from anterior side 12followed by a decrease in height as posterior side 14 is approached. Theimplant has a generally constant height from lateral side 16 to lateralside 18. In another preferred embodiment, the implant may have a gradualincrease in height followed by a gradual decrease in height from lateralside 16 to lateral side 18. The substantially convex curvature of uppersurface 15 and tower surface 30 change the height of implant 10 in theanterior to posterior direction. In another preferred embodiment, thesubstantially convex curvature of upper surface 15 and lower surface 30change the height of implant 10 in the lateral direction. Implant 10preferably has the greatest height generally midway between anteriorside 12 and the center of implant 10. In an exemplary embodiment, uppersurface 15 and lower surface 30 may also be flat planar surfaces or flatangled surfaces. Alternatively, the upper surface 15 and lower surface30 may be substantially curved surfaces, preferably shaped to mimic thetopography of the vertebral end plates.

In order to facilitate insertion of implant 10: posterior side 14 andanterior side 12 transition to upper and lower surfaces 15, 30 withrounded edges 40. Rounded edges 40 may enable implant 10 to slidebetween the end plates while minimizing the necessary distraction of theend plates. In a preferred embodiment, rounded edges 40 have a radius ofcurvature ranging from about 0.75 mm to 1.75 mm, but preferably is about1.25 mm. In another preferred embodiment, rounded edges 40 may extendaround the periphery of implant 10. Rounded edges 40 may also be used asa means to clean the edges of the implant 10 by eliminating any half orpartial teeth located on or near the edge of the implant 10.

As shown in FIG. 2 and FIG. 3, channel 32 runs through implant 10 fromanterior side 12 through central bore 26 to posterior side 14. Channel32 is sized to receive a surgical instrument such as an inserter forimplantation of implant 10. In addition, located along the side ofchannel 32: near anterior side 12, are retaining grooves 34 whichfurther assist with coupling the implantation instrument to implant 10.Using the implantation instrument with channel 32 and retaining grooves34, implant 10 can be inserted in an anterior approach where posteriorend 14 is the first side to be introduced to the intervertebral space.

Extending from a first lateral side 16 to a second lateral side 18 maybe a second instrument receiving channel 38. Channel 38 is also sized toreceive a surgical instrument such as an inserter for implantation ofimplant 10 and has retaining grooves 36 and 37 to further assist withcoupling the implantation instrument to implant 10. Using theimplantation instrument with channel 38 and retaining grooves 36:implant 10 can be inserted in a lateral approach where lateral side 16is the first side to be introduced into the intervertebral space.Alternatively, using the implantation instrument with channel 38 andretaining grooves 37, implant 10 can be inserted in a lateral approachwhere lateral side 18 is the first side to be introduced into theintervertebral space.

Although spinal spacer insertion instruments are well known in the art,an inserter used with implant 10 may be modified to optionally includereleaseable engaging members configured and dimensioned to mate withretaining grooves 34, 36, 37 to further assist with holding the implantduring the insertion and installation procedure.

As can be seen in FIGS. 2 and 3, channel 32 is shown extending theentire length of the lateral sides 16, 18 of the implant 10. However, inan exemplary embodiment, channel 32 may extend only a portion of thelength of lateral sides 16,18, or may extend the length of only one ofthe lateral sides 16, 18. Likewise, channel 38 may extend only a portionof the length of sides 12, 14 or may extend along one of the sides 12,14.

To further assist with the insertion and implantation of implant 10,implant 10 has areas 22 and 24, located on the upper 15 and lower 30surface of implant 10, which are substantially smooth and are sized toreceive an instrument such as a distractor, which is well known in theart. In this particular embodiment, area 22 extends in ananterior-posterior direction helping facilitate anterior implantinsertion and area 24 extends in a transverse or lateral directionhelping facilitate transverse implant insertion. Although in FIG. 1 area22 is shown as extending along the entire longitudinal length of implant10, from the perimeter edge of anterior side 12 to the perimeter edge ofposterior side 14, area 22 may extend only partially along thelongitudinal length of implant 10. The preceding is also applicable toarea 24. Area 24 is shown to extend along the entire transverse lengthof implant 10, however, area 24 may extend only partially along thetransverse length of implant 10. Furthermore, in an exemplaryembodiment, only area 22, as shown in FIG. 4A, or only area 24, as shownin FIG. 4B, may be present on upper and lower surfaces 15, 30 of implant10.

Implant 10 may be fabricated from pure titanium or an alloy thereof,preferably anodized to increase its biocompatibility by making it moreinert. Implant 10 may also be fabricated from a radiolucent material,such as polyetheretherketone or polyetherketoneketone, and may include aradiopaque marker, such as a titanium alloy pin. The radiopaque markermay be located along any of the implant sides such as anterior side 12,posterior side 14 or lateral sides 16, 18. By using a radiolucentmaterial, the progression and status of the fusion can be trackedthrough the use of X-rays or similar devices while the radiopaque markerwill indicate the position of the implant with respect to the adjacentvertebral bodies. Implant 10 may also be fabricated from otherbiocompatible materials, such as allografts, and/or other resorbablematerials.

The dimensions of the implant 10 may vary depending on where in thespine the implant will be inserted. The vertebral bodies in the lumbararea of the spine, for example, are larger than the vertebral bodies inthe thoracic area. Therefore, an implant intended for the thoracicregion would be smaller than one for the lumbar region. Likewise, lowerlumbar disc replacements would be larger than upper ones. A person ofordinary skill could adapt the basic dimensions of the implant to makethem occupy the space formerly occupied by the particular vertebral discwhich needs replacement. Implant 10 is generally sized for anterior,lateral, or anterio-lateral approaches where inserting the implantaround the spinal cord or spinal dural sac is not necessary as in aposterior approach. An exemplary embodiment of implant 10 may have awidth (extending from anterior side 12 to posterior side 14) rangingfrom 15 mm-40 mm, but preferably about 22-26 mm, and most preferablyabout 24 mm, and a length (extending from lateral side 16 to lateralside 18) ranging from 20 mm-50 mm, but preferably about 28-32 mm, andmost preferably about 30 mm. In addition, in an exemplary embodiment,the height of implant 10, measure as the distance between upper surface15 and lower surface 30, when used as an intervertebral spacer, may bein the range of about 5 mm to about 25 mm. When using implant 10 as acorpectomy device, the height of implant 10 may range from about 17 mmto about 100 mm. Furthermore, in an exemplary embodiment, the radius ofcurvature 19 (shown in FIG. 1) of the concave and the radius ofcurvature 17 (shown in FIG. 1) of the convex sides may range from about8 mm to about 30 mm, but preferably are about 13 mm. The radius ofcurvature 21 (shown in FIG. 1) of transition areas 13 which connectconcave side 14 with convex sides 16, 18 may be about 4 mm to about 8mm, but preferably are about 6 mm. Also, in an exemplary embodiment, theradius of curvature of the upper and lower surfaces of implant 10 fromanterior side 12 to posterior side 14 may range from about 40 mm toabout 100 mm, but preferably about 50 mm. The upper and lower surfaces15, 30 are preferably flat between lateral sides 16, 18.

FIG. 5 shows a top view of a second embodiment of an implant 100. Ingeneral, most of the structure of implant 100 is similar or comparableto the structure of implant 10. Accordingly, the equivalent structuresof implant 100 have been numbered the same as implant 10 and discussionof the similar components and features is not believed necessary. Inthis particular embodiment, located on upper surface 15 and lowersurface 30 of implant 100, is area 110. Area 110 extends simultaneouslyin a longitudinal and lateral direction diagonally across implant 110 tofacilitate anterio-lateral implant insertion. Although in FIG. 5 area110 is shown as extending along the entire length of implant 100, area110 may extend only partially along the length of implant 100.

Similar to implant 10 discussed above, implant 100 has the two sets ofinstrument receiving channels to increase surgical flexibility wheninserting implant 100 and to facilitate the insertion process bycreating more surgical insertion alternatives. In the case of ananterio-lateral insertion, either channel 38 with retaining grooves 36and 37 may be used or channel 32 with retaining grooves 34 may be used.

FIG. 9 shows a top view of a third embodiment of an implant 200. Ingeneral, most of the structure of implant 200 is similar or comparableto the structure of implant 10. Accordingly, the equivalent structuresof implant 200 have been numbered the same as implant 10 and discussionof the similar components and features is not believed necessary. Inthis particular embodiment, instead of having instrument receivingchannels, implant 200 has threaded bores 210, 212. Threaded bores 210,212 are sized to receive an implantation instrument such as a threadedinserter.

As can best be seen in FIGS. 10 and 11, threaded bore 210 is located onlateral side 18. This location allows for insertion of implant 200 in alateral fashion. Although, threaded bore 210 is located on lateral side18, it may also be located on lateral side 16. This location also allowsfor insertion of implant 200 in a lateral direction. FIGS. 11 and 12show threaded bore 212 which is located on anterior side 12 of implant200. This location allows for insertion of implant 200 in an anteriordirection with posterior side 14 being the first side to be introducedto the intervertebral space.

FIG. 13 shows a top view of a fourth embodiment of an implant 300. Ingeneral, most of the structure of implant 300 is similar or comparableto the structure of implant 100. Accordingly, the equivalent structuresof implant 300 have been numbered the same as implant 100 and discussionof the similar components and features is not believed necessary. Inthis particular embodiment, instead of having instrument receivingchannels, implant 300 has threaded bore 310. Threaded bore 310, is sizedto receive an implantation instrument such as a threaded inserter.

As can best be seen in FIGS. 15 and 16, threaded bore 310 is located onan anterio-lateral side (between anterior side 12 and lateral side 16)of implant 300. This location allows for insertion of implant 200 in ananterio-lateral fashion. Although, threaded bore 310 is located on ananterio-lateral side (between anterior side 12 and lateral side 16), itcan also be located on an opposite anterio-lateral side (betweenanterior side 12 and lateral side 18) also allowing for ananterio-lateral implantation.

In a fifth embodiment, implant 400 is similar to the previouslydisclosed embodiment but now has a stackability feature. As will befurther explained below, implant 400 includes an upper endcap and alower endcap which may be stacked to form the spacer or implant. Asshown in FIG. 16A, implant 400 may also include at least one bodyportion which may be stacked between the upper endcap and the lowerendcap to form the spacer or implant. FIG. 17 shows a top view of upperendcap 402 of implant 400. Upper endcap 402 has a generally kidney-beanshaped footprint which includes anterior side 403, posterior side 404,and first and second lateral sides 406, 408. Anterior side 403 andlateral sides 406, 408 are alt substantially arcuate, preferably convex,in shape while posterior side 404 is substantially arcuate, preferablyconcave, in shape.

As shown in FIGS. 17-20, upper endcap 402 also includes two elongatedbores 410 which can be filled with bone growth inducing substances toallow bony ingrowth and to further assist in the fusion of the adjacentvertebrae. Upper endcap 402 further includes a central bore 411 forreceiving a fastening member such as a screw. In addition upper endcap402, on its upper surface 405, has sections or areas having teeth 412 orsimilar gripping means to facilitate engagement of implant 400 with theend plates of the adjacent vertebra, and has sections or areas 414, 416which are substantially smooth and devoid of any protrusions. Althoughin FIG. 17 sections 414, 416 are shown as extending along the entirelength of upper endcap 402, from perimeter edge to perimeter edge,sections 414, 416 may extend only partially along the length of upperendcap 402. Sections 414, 416 are provided to assist the surgeon inanterior or lateral implantation of the implant as was discussed abovewith respect to sections 22, 24. As can be seen in FIGS. 18 and 21,upper endcap 402 has a generally rectangular protrusion 418 configuredand dimensioned to interface and mate with a recess portion of theimplant body or with the lower endcap. While protrusion 418 has beenshown and described as generally rectangular, it can be appreciated thatprotrusion 418 can be any shape desired. A lower surface 407 surroundsthe protrusion 418. Lower surface 407 is illustrated as surrounding andencircling completely protrusion 418, but it can be appreciated thatlower surface 407 may only partially surround protrusion 418.

Upper endcap 402 may have a generally wedge-shaped, side profile that isdesigned to restore the natural curvature or lordosis of the spine afterthe affected disc or affected vertebral body and adjoining discs havebeen removed. As shown in FIG. 19, this wedge shape results from agradual increase in height from anterior side 403 followed by a decreasein height as posterior side 404 is approached. The substantially convexcurvature of upper surface 405 changes the height of implant 400 alongits width. In an exemplary embodiment, upper surface 405 may also be aflat planar surface, a flat angled surface, or a substantially curvedsurface, preferably shaped to mimic the topography of the adjacentvertebral end plates. The radius of curvature for upper surface 405 maybe the same as described for the one-piece implant described earlier.

FIG. 22 shows a top view of a lower endcap 420. In general, most of thestructure of endcap 420 is similar or comparable to the structure ofendcap 402. Accordingly, the equivalent structures of endcap 420 havebeen numbered the same as endcap 402 and discussion of the similarcomponents and features is not believed necessary. As discussed withendcap 402, endcap 420 also has a generally kidney-bean shaped footprintwhich includes anterior side 403, posterior side 404, and first andsecond lateral sides 406, 408. Anterior side 403 and lateral sides 406,408 are all substantially arcuate, preferably convex, in shape whileposterior side 404 is substantially arcuate, preferably concave, inshape. As can be seen in FIGS. 37-41, on lower surface 407, lower endcap420 has a shoulder 424 defining a cavity 422 configured and dimensionedto interface and mate with a portion of the implant body. Shoulder 424has been shown as surrounding cavity 422 entirely, but it should beappreciated that shoulder 424 may only partially surround cavity 422.

Turning now to FIGS. 27-31, an alternative embodiment of upper endcap430 can be seen. In general, most of the structure of upper endcap 430is similar or comparable to the structure of upper endcap 402.Accordingly, the equivalent structures of upper endcap 430 have beennumbered the same as upper endcap 402 and discussion of the similarcomponents and features is not believed necessary. In this particularembodiment, located on upper surface 405 of upper endcap 430, is area432. Area 432 extends simultaneously in a longitudinal and lateraldirection diagonally across upper endcap 430 to facilitateanterio-lateral implant insertion. Although in FIGS. 27-31, area 432 isshown as extending along the entire length of upper endcap 430, area 432may extend only partially along the length of upper endcap 430.

FIG. 32 shows a top view of a lower endcap 440. In general, most of thestructure of lower endcap 440 is similar or comparable to the structureof lower endcap 420. Accordingly, the equivalent structures of lowerendcap 440 have been numbered the same as lower endcap 420 anddiscussion of the similar components and features is not believednecessary. As can be seen in FIGS. 32-36, located on lower surface 405of lower endcap 440, is area 432. Area 432 extends simultaneously in alongitudinal and lateral direction diagonally across lower endcap 440 tofacilitate anterio-lateral implant insertion. Although in FIGS. 32-35,area 432 is shown as extending along the entire length of lower endcap440, area 432 may extend only partially along the length of upper endcap440.

FIG. 37 shows a front or anterior view of a body portion 450. Ingeneral, some of the structure of body portion 450 is similar orcomparable to the structure of upper and lower endcaps 402, 420, 430,440. Accordingly, the equivalent structures of body portion 450 havebeen numbered the same as upper and lower endcaps 402, 420, 430, 440 anddiscussion of the similar components and features is not believednecessary. As can be seen in FIGS. 37-40, body portion 450 has agenerally kidney-bean shape footprint. Located on upper surface 455,body portion 450 has a shoulder 462 defining a cavity 464 and located onlower surface 457, body portion 450 has a generally rectangularprotrusion 456. While shoulder 462 is shown as completely enclosing andsurrounding cavity 464, shoulder 462 may only partially surround cavity464. Likewise, lower surface 457 is shown as completely surroundingprotrusion 456, but it can be appreciated that lower surface 457 mayonly partially surround protrusion 456. Shoulder 462 and cavity 464 areconfigured and dimensioned to interface and mate with either rectangularprotrusion 418 of upper endcaps 402, 430 or rectangular protrusion 456of another body portion 450. Protrusion 456 of body portion 450 isconfigured and dimensioned to interface and mate with either cavity 422of lower end plates 420, 440 or cavity 464 of another body portion 450.Again, while the protrusions have been described as rectangular, anygeometric shape is contemplated.

As mentioned above, implant 400 is a stackable implant comprising anupper endcap 402, 430, a lower endcap 420, 440, and, if necessary, atleast one body portion 450. It is also possible for implant 400 toinclude an upper endcap 402, 430 and a lower endcap 420, 440. Themodularity of implant 400, allows implant 400 to have a variable height,thereby allowing a surgeon to create an implant sized to appropriatelyfit the surgical space. In use, once the implant height that will beneeded for the surgical procedure is determined, the desired implant canbe created from the endcaps and, if necessary, one or more bodyportions. If a smaller implant is needed, implant 400 may comprise upperendcap 402, 430, and lower endcap 420, 440. If a larger implant isneeded, implant 400 may comprise upper endcap 402, 430, lower endcap420, 440 and at least one body portion 450. Body portions 450 may be thesame size or of various sizes. Upper and lower endcaps 402, 420, 430,440 and body portion 450 are configured and dimensioned to mate witheach other via an interference or similar fit. For further fixation ofthe endcaps and body portion together, a fixation screw may be threadedinto central bore 411. Additional screws and bores my also be used.

Body portion 450 also may include channels 464, 466 or threaded bores458, 460 for implantation of the assembled implant 400. Channel 464 runsanterior to posterior through body portion 450 from anterior side 403 toposterior side 404. Channel 464 is sized to receive a surgicalinstrument such as an inserter for implantation of implant 400. Usingthe implantation instrument, implant 400 can be inserted in a lateralapproach where the contra-lateral side is the first side to beintroduced into the intervertebral space. Alternatively, using theimplantation instrument with channel 464, implant 400 may be inserted ina lateral approach where lateral side 408 is the first side to beintroduced to the intervertebral space.

Extending from a first lateral side 406 to a second lateral side 408 maybe a second instrument receiving channel 466 (not shown). Channel 466 isalso sized to receive a surgical instrument such as an inserter forimplantation of implant 400. Using the implantation instrument withchannel 466, implant 400 may be inserted in an anterior approach whereposterior end 404 is the first side to be introduced to theintervertebral space.

Although channel 464 is described as extending the entire length of thelateral sides 406, 408 of the implant 400, channel 464 may extend only aportion of the length of lateral sides 406,408, or may extend the lengthof only one of the lateral sides 406, 408. Likewise, channel 466 mayextend the length of one of the sides 403, 404 or may extend only aportion of the length of sides 403, 404.

Implant 400, instead of having instrument receiving channels, may havethreaded bores 458, 460. Threaded bores 458, 460 are sized to receive animplantation instrument such as a threaded inserter.

As can best be seen in FIGS. 37 and 41, threaded bore 458 is located onlateral side 406. This location allows for insertion of implant 400 in alateral fashion. Although, threaded bore 458 is located on lateral side406, it may also be located on lateral side 408. This location alsoallows for insertion of implant 400 in a lateral direction. FIG. 41shows threaded bore 460 which is located on anterior side 403 of implant400. This location allows for insertion of implant 400 in an anteriordirection with posterior side 404 being the first side to be introducedto the intervertebral space.

In a sixth embodiment, implant 500 is similar to the previouslydisclosed stackable embodiment, however implant 500 has a differentcoupling configuration for stacking. As will be further explained below,implant 500 includes a plurality of endcaps which may be stacked to formthe spacer or implant. Implant 500 may also include at least one bodyportion which may be stacked between the endcaps to form the implant.FIG. 42 shows a top view of endcap 502 of implant 500. Endcap 502 has agenerally kidney-bean shaped footprint which includes anterior side 503,posterior side 504, and first and second lateral sides 506, 508.Anterior side 503 and lateral sides 506, 508 are all substantiallyarcuate, preferably convex, in shape while posterior side 504 issubstantially arcuate, preferably concave, in shape.

As shown in FIGS. 42-46, endcap 502 also includes two elongated bores510 which can be filled with bone growth inducing substances to allowbony ingrowth and to further assist in the fusion of the adjacentvertebrae. Endcap 502 further includes a central bore 511 for receivinga fastening member, such as a screw, sleeve, or nut. In addition, endcap502, on its upper surface 505, has sections or areas having grippingstructures 512 to facilitate engagement of implant 500 with the endplates of the adjacent vertebra, and has sections or areas 516 which aresubstantially smooth and devoid of any protrusions. Although in FIG. 42sections 516 are shown as extending along the entire length of endcap502, from perimeter edge to perimeter edge, sections 516 may extend onlypartially along the length of endcap 502. Sections 516 are provided toassist the surgeon in anterior or lateral implantation of the implant aswas discussed above with respect to section 22. As can be seen in FIGS.43 and 46, endcap 502 has a generally rectangular protrusion 518configured and dimensioned to interface and mate with a recess portionof the implant body or another endcap. While protrusion 518 has beenshown and described as generally rectangular, it can be appreciated thatprotrusion 518 can be any shape desired. A lower surface 507 surroundsthe protrusion 518. Lower surface 507 is illustrated as surrounding andencircling completely protrusion 518: but it can be appreciated thatlower surface 507 may only partially surround protrusion 518. Locatedproximate to protrusion 518, on lower surface 507: is a shoulder 515defining a cavity 513. Cavity 513 is configured and dimensioned tointerface and mate with a portion of the implant body or another endcap.Shoulder 515 has been shown as surrounding cavity 513 entirely, but itshould be appreciated that shoulder 515 may only partially surroundcavity 513. This different coupling configuration allows forinterchangeability of the endcaps.

Endcap 502 may have a generally wedge-shaped, side profile that isdesigned to restore the natural curvature or lordosis of the spine afterthe affected disc or affected vertebral body and adjoining discs havebeen removed. As shown in FIG. 44, this wedge shape results from agradual increase in height from anterior side 503 followed by a decreasein height as posterior side 504 is approached. The substantially convexcurvature of upper surface 505 changes the height of implant 500 alongits width. In an exemplary embodiment, upper surface 505 may also be aflat planar surface, a flat angled surface, or a substantially curvedsurface, preferably shaped to mimic the topography of the adjacentvertebral end plates. The radius of curvature for upper surface 505 maybe the same as described for the one-piece implant described earlier.

FIG. 47 shows a top view of another endcap 520. In general, most of thestructure of endcap 520 is similar or comparable to the structure ofendcap 502. Accordingly, the equivalent structures of endcap 520 havebeen numbered the same as endcap 502 and discussion of the similarcomponents and features is not believed necessary. As discussed withupper endcap 502, endcap 520 also has a generally kidney-bean shapedfootprint which includes anterior side 503, posterior side 504, andfirst and second lateral sides 506, 508. Anterior side 503 and lateralsides 506, 508 are all substantially arcuate, preferably convex, inshape while posterior side 504 is substantially arcuate, preferablyconcave, in shape. As can be seen in FIGS. 47-51, endcap 520 alsoincludes two elongated bores 510 which can be filled with bone growthinducing substances to allow bony ingrowth and to further assist in thefusion of the adjacent vertebrae, Endcap 520 further includes a centralbore 511 for receiving a fastening member, such as a screw, sleeve ornut. In addition, endcap 520, on its upper surface 505, has sections orareas having gripping structures 512 to facilitate engagement of implant500 with the end plates of the adjacent vertebra, and has sections orareas 517 which are substantially smooth and devoid of any protrusions.Although in FIG. 47 sections 517 are shown as extending along the entirelength of endcap 520, from perimeter edge to perimeter edge, sections517 may extend only partially along the length of endcap 520. Sections517 are provided to assist the surgeon in transverse implantation of theimplant as was discussed above with respect to section 24. As can beseen in FIGS. 48 and 51, endcap 520 has a generally rectangularprotrusion 518 configured and dimensioned to interface and mate with arecess portion of the implant body or another endcap. While protrusion518 has been shown and described as generally rectangular, it can beappreciated that protrusion 518 can be any shape desired. A lowersurface 507 surrounds the protrusion 518. Lower surface 507 isillustrated as surrounding and encircling completely protrusion 518, butit can be appreciated that lower surface 507 may only partially surroundprotrusion 518. Located proximate to protrusion 518, on lower surface507, is a shoulder 515 defining a cavity 513. Cavity 513 is configuredand dimensioned to interface and mate with a portion of the implant bodyor another endcap. Shoulder 515 has been shown as surrounding cavity 513entirely, but it should be appreciated that shoulder 515 may onlypartially surround cavity 513.

Endcap 520 may have a generally wedge-shaped, side profile that isdesigned to restore the natural curvature or lordosis of the spine afterthe affected disc or affected vertebral body and adjoining discs havebeen removed. As shown in FIG. 49, this wedge shape results from agradual increase in height from anterior side 503 followed by a decreasein height as posterior side 504 is approached. The substantially convexcurvature of upper surface 505 changes the height of implant 500 alongits width. In an exemplary embodiment, upper surface 505 may also be aflat planar surface, a flat angled surface, or a substantially curvedsurface, preferably shaped to mimic the topography of the adjacentvertebral end plates. The radius of curvature for upper surface 505 maybe the same as described for the one-piece implant described earlier.

Turning now to FIGS. 52-56, an alternative embodiment of endcap 530 canbe seen. In general, most of the structure of endcap 530 is similar orcomparable to the structure of endcap 502. Accordingly, the equivalentstructures of endcap 530 have been numbered the same as endcap 502 anddiscussion of the similar components and features is not believednecessary. In this particular embodiment, located on upper surface 505of endcap 530, is area 519. Area 519 extends simultaneously in alongitudinal and lateral direction diagonally across endcap 530 tofacilitate anterio-lateral implant insertion. Although in FIGS. 52-56,area 519 is shown as extending along the entire length of endcap 530,area 519 may extend only partially along the length of endcap 530.

FIG. 57 shows a top view of a body portion 550. In general, some of thestructure of body portion 550 is similar or comparable to the structureof endcaps 502, 520, and 530. Accordingly, the equivalent structures ofbody portion 550 have been numbered the same as endcaps 502, 520, and530 and discussion of the similar components and features is notbelieved necessary. As can be seen in FIGS. 57-62, body portion 550 hasa generally kidney-bean shape footprint. Located on upper surface 555and lower surface 557, body portion 550 has a shoulder 562 defining acavity 564 and a generally rectangular protrusion 556. While shoulder562 is shown as completely enclosing and surrounding cavity 564,shoulder 562 may only partially surround cavity 564. Likewise, uppersurface 555 and lower surface 557 are shown as completely surroundingprotrusions 556, but it can be appreciated that upper surface 555 andlower surface 457 may only partially surround protrusions 556. Shoulder562 and cavity 564 are configured and dimensioned to interface and matewith either rectangular protrusion 518 of endcaps 502, 520, 530 orrectangular protrusion 556 of another body portion 550. Protrusion 556of body portion 550 is configured and dimensioned to interface and matewith either cavity 513 of endcaps 502, 520, 530 or cavity 564 of anotherbody portion 550. Again, while the protrusions have been described asrectangular, any geometric shape is contemplated.

As mentioned above, implant 500 is a stackable implant comprising twoendcaps 502, 520, 530, and, if necessary, at least one body portion 550.The modularity of implant 500, allows implant 500 to have a variableheight, thereby allowing a surgeon to create an implant sized toappropriately fit the surgical space. In use, once the implant heightthat will be needed for the surgical procedure is determined, thedesired implant can be created from the endcaps and, if necessary, oneor more body portions. If a smaller implant is needed, implant 500 maycomprise two endcaps 502, 520, 530. If a larger implant is needed,implant 500 may comprise endcaps 502, 520, 530, and at least one bodyportion 550. Body portions 550 may be the same size or of various sizes.Endcaps 502, 520, 530, and body portion 550 are configured anddimensioned to mate with each other via an interference or similar fit.For further fixation of the endcaps or the endcaps and body portiontogether, a fixation screw may be threaded into central bore 511.Additional screws and bores my also be used.

Body portion 550 also may include channels 563, 566 and/or threadedbores 558, 560 for implantation of the assembled implant 500. Channel563 runs anterior to posterior through body portion 550 from anteriorside 503 to posterior side 504. Channel 563 is sized to receive asurgical instrument such as an inserter for implantation of implant 500.Using the implantation instrument, implant 500 can be inserted in alateral approach where the contra-lateral side is the first side to beintroduced into the intervertebral space. Alternatively, using theimplantation instrument with channel 563, implant 500 may be inserted ina lateral approach where lateral side 508 is the first side to beintroduced to the intervertebral space.

Extending from a first lateral side 506 to a second lateral side 508 maybe a second instrument receiving channel 566. Channel 566 is also sizedto receive a surgical instrument such as an inserter for implantation ofimplant 500. Using the implantation instrument with channel 566, implant500 may be inserted in an anterior approach where posterior end 504 isthe first side to be introduced to the intervertebral space.

Although channel 563 is described as extending the entire length of thelateral sides 506, 508 of the implant 500, channel 563 may extend only aportion of the length of lateral sides 506,508, or may extend the lengthof only one of the lateral sides 506, 508. Likewise, channel 566 mayextend the length of one of the sides 503, 504 or may extend only aportion of the length of sides 503, 504.

Implant 500, instead of or in addition to having instrument receivingchannels, may have threaded bores 558, 560. Threaded bores 558, 560 aresized to receive an implantation instrument such as a threaded inserter.

As can best be seen in FIGS. 59, 61 and 62, threaded bore 558 is locatedon lateral sides 506, 508. This location allows for insertion of implant500 in a lateral fashion. FIG. 59 shows threaded bore 560 which islocated on anterior side 503 of implant 500. This location allows forinsertion of implant 500 in an anterior direction with posterior side504 being the first side to be introduced to the intervertebral space.

As can best be seen in FIG. 59, body portion 550 may also includeopenings 561, which preferably extend from the outer surface of bodyportion 550 to elongated bores 510. Openings 561 may be packed with bonegrowth inducing substances to further aid in the fixation and fusion ofthe implant.

In a seventh embodiment, implant 600 is similar to the previouslydisclosed stackable embodiment, however implant 600 has a slightlydifferent structure and footprint. Preferably, the structure andfootprint of implant 600 allows implant 600 to be particularly suitedfor implantation in the cervical region of the spine. FIG. 63 shows atop view of endcap 602 of implant 600. Endcap 602 has a generally oblongoctagonal shaped footprint which includes anterior side 603, posteriorside 604, and first and second lateral sides 606, 608.

As shown in FIGS. 63-66, endcap 602 also includes an elongated bore 610which can be filled with bone growth inducing substances to allow bonyingrowth and to further assist in the fusion of the adjacent vertebrae.Endcap 602 further includes a central bore 611 for receiving a fasteningmember, such as a screw. In addition, endcap 602, on its upper surface605, has sections or areas having gripping structures 612 to facilitateengagement of implant 600 with the end plates of the adjacent vertebra,and has sections or areas 616 which are substantially smooth and devoidof any protrusions. Although in FIG. 63 section 616 is shown asextending along a partial length of endcap 602, sections 616 may extendalong the entire length of endcap 602, from perimeter edge to perimeteredge. Section 616 may be provided to provide a recess allowing a screwhead to be recessed so as not to extend upwardly beyond the upper endsof the gripping structures 612. As can be seen in FIGS. 65 and 66,endcap 602 has a protrusion 618 configured and dimensioned to interfaceand mate with a recess portion of the implant body or another endcap. Itcan be appreciated that protrusion 618 may be any shape desired. A lowersurface 607 surrounds the protrusion 618. Lower surface 607 isillustrated as surrounding and encircling completely protrusion 618, butit can be appreciated that lower surface 607 may only partially surroundprotrusion 618. Located proximate to protrusion 618, on lower surface607, is a shoulder 615 defining a cavity 613. Cavity 613 is configuredand dimensioned to interface and mate with a portion of the implant bodyor another endcap. Shoulder 615 has been shown as surrounding cavity 613entirely, but it should be appreciated that shoulder 615 may onlypartially surround cavity 513.

Endcap 602 may have a generally wedge-shaped, side profile that isdesigned to restore the natural curvature or lordosis of the spine afterthe affected disc or affected vertebral body and adjoining discs havebeen removed. As shown in FIG. 66, this wedge shape results from agradual increase in height from anterior side 603 to the posterior side604. In an exemplary embodiment, upper surface 605 may also be a flatplanar surface, a convexly-curved surface, or a substantially curvedsurface, preferably shaped to mimic the topography of the adjacentvertebral end plates. The radius of curvature for upper surface 605 maybe the same as described for the one-piece implant described earlier.

FIG. 67 shows a top view of a body portion 650. In general, some of thestructure of body portion 650 is similar or comparable to the structureof endcap 602. Accordingly, the equivalent structures of body portion650 have been numbered the same as endcap 602 and discussion of thesimilar components and features is not believed necessary. As can beseen in FIGS. 67-69, body portion 650 has a generally oblong octagonalshape footprint. Located on upper surface 655 and lower surface 657,body portion 650 has a shoulder 662 defining a cavity 664 and aprotrusion 656. While shoulder 662 is shown as completely enclosing andsurrounding cavity 664, shoulder 662 may only partially surround cavity664. Likewise, upper surface 655 and lower surface 657 are shown ascompletely surrounding protrusions 656, but it can be appreciated thatupper surface 655 and lower surface 657 may only partially surroundprotrusions 656. Shoulder 662 and cavity 664 are configured anddimensioned to interface and mate with either protrusion 618 of endcap602, or protrusion 656 of another body portion 650. Protrusion 656 ofbody portion 650 is configured and dimensioned to interface and matewith either cavity 613 of endcaps 602 or cavity 664 of another bodyportion 650. Again, the protrusions may be any contemplated geometricshape.

As mentioned above, implant 600 is a stackable implant comprising twoendcaps 602, and, if necessary, at least one body portion 650. Themodularity of implant 600, allows implant 600 to have a variable height,thereby allowing a surgeon to create an implant sized to appropriatelyfit the surgical space. In use, once the implant height that will beneeded for the surgical procedure is determined, the desired implant canbe created from the endcaps and, if necessary, one or more bodyportions. If a smaller implant is needed, implant 600 may comprise twoendcaps 602. If a larger implant is needed, implant 600 may compriseendcaps 602, and at least one body portion 650. Body portions 650 may bethe same size or of various sizes. Endcap 602, and body portion 650 areconfigured and dimensioned to mate with each other via an interferenceor similar fit. For further fixation of the endcaps or the endcaps andbody portion together, a fixation screw may be threaded into centralbore 611. Additional screws and bores my also be used.

Body portion 650 also may include windows 665, 666 which can be filledwith bone growth inducing substances to further allow for bony ingrowthand to further assist in the fusion of the adjacent vertebrae. Windows665, 666 may also be used to mate with the implant holder to assist withthe implantation of the implant.

Body portion 650 may also have a threaded bore 658. Threaded bore 658 issized to receive an implantation instrument such as a threaded inserterfor implantation of the assembled implant 600. As can best be seen inFIG. 69, threaded bore 558 is located on lateral sides 606, 608. Thislocation allows for insertion of implant 600 in a lateral fashion.

FIG. 70 shows a perspective view of one embodiment of implant 600 whichincludes two endcaps 602 and one body portion 650.

The embodiments disclosed herein are illustrative and exemplary innature and it will be appreciated that numerous modifications and otherembodiments of the implant disclosed may be devised by those skilled inthe art.

The invention claimed is:
 1. An intervertebral implant assemblycomprising: an intervertebral implant, the intervertebral implantcomprising a body having a convexly curved anterior side substantiallyopposing a posterior side spaced apart by first and second lateralsides; top and bottom surfaces defining two central bores extending fromeach surface through to the other, wherein each of the top and bottomsurfaces are configured to contact an endplate of adjacent vertebrae,and wherein each of the top and bottom surfaces have a plurality ofgripping structures for engaging the endplates of the adjacent vertebraeand have a substantially smooth recessed area extending from an outerperiphery of the implant and at least partially intersecting with atleast one of the two central bores; and at least two separate channelsformed in the implant, wherein at least one of the two separate channelsextends to or into each of the two central bores; and a surgicalinstrument received in the substantially smooth recessed areas of thetop and bottom surfaces; wherein the substantially smooth recessed areaof the top surface extends in an anterior-posterior direction from afirst perimeter edge where the top surface intersects with the anteriorsurface of the implant to a second perimeter edge where the top surfaceintersects with the posterior surface of the implant; and wherein thesubstantially smooth recessed area of the bottom surface extends in ananterior-posterior direction from a first perimeter edge where thebottom surface intersects with the anterior surface of the implant to asecond perimeter edge where the bottom surface intersects with theposterior surface of the implant.
 2. The assembly of claim 1 wherein atleast one side of the intervertebral implant has a third channel forreceiving an insertion instrument.
 3. The assembly of claim 1 wherein atleast one channel of the at least two separate channels runs in at leastan anterior-posterior direction or a lateral direction.
 4. The assemblyof claim 1 further comprising an insertion instrument, wherein at leastone channel of the at least two separate channels contains at least oneretaining groove to assist with coupling the insertion instrument to theimplant.
 5. The assembly of claim 4 wherein the insertion instrument hasa releasable engaging member to mate with the retaining grove.
 6. Theassembly of claim 1 wherein at least one channel of the at least twoseparate channels comprises a threaded bore.
 7. The assembly of claim 6further comprising a threaded inserter configured to engage the threadedbore.
 8. The assembly of claim 1 wherein the surgical instrument is adistractor.
 9. The assembly of claim 1 wherein at least one channel ofthe at least two separate channels runs in an anterior-posteriordirection or a lateral direction.
 10. The assembly of claim 1 whereinthe top and bottom surfaces of the implant are substantially flat planarsurfaces having a downward taper at an anterior end of the implant andat a posterior end of the implant to facilitate insertion of theimplant.
 11. The assembly of claim 1 wherein the top surface and thebottom surface of the implant define a height dimension h₁ at theposterior side and a height dimension h₂ at the anterior side, whereinh₂ is larger than h₁.
 12. The assembly of claim 11 wherein the topsurface and the bottom surface of the implant define a height dimensionh₃ at an intermediate point between the anterior side and the posteriorside, h₃ being larger than h₂.
 13. The assembly of claim 1, wherein theplurality of gripping structures sit proud of the substantially smoothrecessed area.
 14. An intervertebral implant kit comprising: anintervertebral implant, the intervertebral implant comprising a bodyhaving a convexly curved anterior side substantially opposing aposterior side spaced apart by first and second lateral sides; top andbottom surfaces defining two central bores extending from each surfacethrough to the other, wherein each of the top and bottom surfaces areconfigured to contact an endplate of adjacent vertebrae, wherein the topsurface and the bottom surface of the implant define a height dimensionh₁ at the posterior side and a height dimension h₂ at the anterior side,wherein h₂ is larger than h₁, and wherein each of the top and bottomsurfaces have a plurality of protrusions projecting out of each of thetop and bottom surfaces for engaging the endplates of the adjacentvertebrae and have a plurality of substantially smooth recessed areasextending from an outer periphery of the implant and at least partiallyintersecting with at least one of the two central bores, one of theplurality of substantially smooth recessed areas on each of the top andbottom surfaces extending across an entire dimension of the implant fromperimeter edge to perimeter edge in an anterior-posterior direction andbeing configured to receive a surgical instrument therein; and at leasttwo separate channels formed in the implant, wherein at least one of thetwo separate channels extends to or into each of the two central bores;and an insertion instrument configured to engage one of the at least twoseparate channels.
 15. The kit of claim 14 wherein at least one channelof the at least two separate channels contains at least one retaininggroove to assist with coupling the insertion instrument to the implant.16. The kit of claim 15 wherein the insertion instrument has areleasable engaging member to mate with the retaining grove.
 17. The kitof claim 14 wherein at least one channel of the at least two separatechannels comprises a threaded bore.
 18. The kit of claim 17 wherein theinsertion instrument is a threaded inserter.
 19. The kit of claim 14 thekit further comprising a distractor wherein the plurality ofsubstantially smooth recessed areas extending in the anterior-posteriordirection receives the distractor.
 20. The kit of claim 14, wherein theplurality of protrusions sit proud of the plurality of substantiallysmooth recessed areas.
 21. An intervertebral implant comprising: aconvexly curved anterior side substantially opposing a posterior sidespaced apart by first and second lateral sides; top and bottom surfacesdefining two central bores extending from each surface through to theother, wherein each of the top and bottom surfaces are configured tocontact an endplate of adjacent vertebrae, and wherein each of the topand bottom surfaces have a plurality of protrusions for gripping theendplates of the adjacent vertebrae and have a plurality ofsubstantially smooth areas recessed from the protrusions and beingconfigured to receive a surgical instrument therein; the plurality ofsubstantially smooth areas extending from an outer periphery of theimplant and at least partially intersecting with at least one of the twocentral bores at least one channel formed in the implant and configuredto engage an implantation instrument; wherein one of the plurality ofsubstantially smooth areas on each of the top and bottom surfacesextends in an anterior-posterior direction from an anterior edge of theimplant to a posterior edge of the implant.
 22. The implant of claim 21,wherein the at least one channel comprises a threaded bore.
 23. Theimplant of claim 21, wherein a second one of the plurality ofsubstantially smooth areas on each of the top and bottom surfacesextends in a lateral direction.
 24. The implant of claim 21, wherein theplurality of protrusions sit proud of the plurality of substantiallysmooth areas.
 25. An implant assembly comprising the implant of claim 21and a surgical instrument received within a first one of the pluralityof substantially smooth areas on the top surface and a second one of theplurality of substantially smooth areas on the bottom surface.